In a steering device having a steering lock device, when an ignition key is turned into a lock position and pulled out from the key hole, a lock pin projects toward the axis of the steering shaft. As a result, an end portion of the lock pin engages a key lock hole formed in a key lock collar press-fitted to the outer periphery of the steering shaft so as to fix the steering shaft to the outer column not to allow the steering shaft to rotate.
Existing steering devices having a steering lock device have a separate housing for the steering lock device bolted to a flange section of an outer column after the housing is positioned by fitting an engaging convex part of the housing in a through hole formed in the outer column.
There have also been steering devices having a steering lock device in which an outer column has a slit used to contract the diameter of the outer column so as to telescopically clamp the outer column to an inner column.
In cases where, in a steering device having both a steering lock device and a telescopic clamp device as described above, a through hole and a slit are closely positioned on an outer column, the outer column strength reduces. Therefore, when, in such cases, the steering wheel is subjected to a large rotating torque in a key-locked state (a lock pin is engaged with a key lock hole), the bending moment applied to the lock pin causes a large stress to be applied to the outer column possibly causing the outer column to be cracked.
In the steering device disclosed in Japanese Unexamined Patent Application Publication No. 2002-337663, a flange section made of thick steel plate is welded to a column made of a steel pipe enhancing the mounting rigidity between the column and the housing for a steering lock device. Also, in the steering device, an engaging convex part of the steering lock device is tightly fitted in a through hole formed in the column, and the bending moment applied to the lock pin in a key-locked state is born by both the flange section and the through hole. The column used in the steering device disclosed in Japanese Unexamined Patent Application Publication No. 2002-337663, is, however, made of steel, and no measure for enhancing the strength of a column made of an aluminum alloy and having both a through hole and a slit is disclosed.
In the steering device disclosed in International Publication WO2006/011378, to secure the strength of a portion peripheral to a slit formed in a column which is made of an aluminum alloy and which has both a through hole and the slot, a rib is formed along the peripheral edge of the closed end of the slit. International Publication WO2006/011378, however, includes no description of a flange section used to attach a housing for a steering lock device to the column.